For me its Berserk, the only manga I've read over and over (partly because he takes so damn long to update it I have to keep reading it to make sure the next chapter doesn't make me feel like it's a random event)

For me, Rave Master is something I can read over and over again, though some of the final arcs are a little stale compared to the first 2/3 and finale arc of the series. Other than that, I feel I can read Fullmetal Alchemist, Fairy Tail, and some of the good story arcs of Naruto (after time skip).